This invention relates to a manually operated control mechanism and is particularly directed toward a device in which a first actuator may be used to preposition a control arm at a desired setting while a second actuator may temporarily reposition the control arm at a different setting without disturbing the setting achieved by the first actuator. The control mechanism includes an anti-creep device so that the selected position of the first actuator is not disturbed by vibration or shocks which might otherwise dislodge the controlled parts from their locked positions.
The invention is particularly applicable to various devices where a manually actuated lever is employed to adjust a mechanical linkage or the like at a predetermined position while retaining the capability to reposition the mechanical linkage temporarily. It is particularly applicable to engine governors and it is shown and described herein as so used for purposes of illustration.
It is conventional practice to employ a governor to maintain a constant engine speed under varying load conditions particularly in heavy earthmoving equipment, where generally a compression type ignition engine is used. Various types of governors used in such applications are generally well-known in the art. A governor representative of the type herein considered is found in U.S. Pat. No. 2,961,229 assigned to the assignee of this invention. Generally, governors of the type herein described utilize a spring loaded device and a control lever to tension the governor spring. Particular tensioning of the governor spring determines the operating speed of the engine. In operation of heavy earthworking equipment it is desirable to position the governor setting at a particular engine speed to produce a particular operating speed over the ground while retaining a capability to slow the engine for brief periods without disturbing the governor setting.
Various schemes have been utilized to accomplish such a constant speed setting, but in most cases the schemes have proved complicated and in some cases cumbersome. In the operation of heavy construction equipment, it is extremely desirable to provide an operating scheme for the vehicle which allows the operator to devote his attention to the job at hand. Thus, simplicity of controls is of great importance. Use of the more complex governor control systems presently available may require diversion of operator attention from the task at hand. Furthermore, these complex systems generally have a high initial cost. Therefore, it is desirable to provide a governor control linkage which is of the simplest design and requires the least amount of operator attention.